This invention relates to tree cutting equipment of a type that may be incorporated into the tree cutting and grasping head of a tree harvester.
Tree cutting equipment for use with a tree harvester where the cutting implement is a shear or a chain saw is well known. It also is known to incorporate both a shear and a chain saw into the same head.
In U.S. Pat. No. 3,976,111, issued Aug. 24, 1976, B. Jonsson there is disclosed a tree cutting device employing both a shear and a chain saw. The shear is mounted at and travels at an acute angle to the kerf made by the saw. In operation, the trunk of a tree is partly cut by the chain saw. The chain saw then is backed out through the saw kerf and the shear is activated to complete the cut. Because of the way in which the shear is inclined, it alone could not be used to cut through the trunk of the tree.
Similar tree cutting equipment is shown in U.S. Pat. No. 3,610,301, issued Oct. 5, 1951, B. L. Jordan. In this case the chain saw and shear move in the same plane, but the degree of movement of the shear is such that it alone could not be used to cut completely through the trunk of the tree. Also this equipment suffers from the disadvantage that the operator must control the depth of the cut made by the chain saw. If the cut is made too deep, the saw may bind making it impossible to withdraw the saw through the saw kerf.
In U.S. Pat. No. 3,796,242, issued Mar. 12, 1974, A. Albright there is disclosed tree cutting equipment including a shear and a chain saw. The cutting implements operate independently of each other depending on tree size, the chain saw being used to cut through large diameter tree trunks and the shears being used with smaller diameter tree trunks. They are not used together in the cutting down of any tree.
In the case of trees which are to be used for lumber, it is desirable that no splitting of the end of the trunk take place when the tree is cut. This requirement dictates that a chain saw should be used. Likewise, in the case of trees having large diameter trunks, say, 8" and over, a chain saw may have to be used. However, with smaller diameter trunks, and where splitting is not a consideration, as in the case of trees slated for use in the pulp and paper industry, it is faster and more economical to cut using a shear.
In accordance with the instant invention there is provided tree cutting equipment employing both a saw and shear. The components are so arranged that the shear alone may be used for cutting through the trunks of certain types of trees, while both the saw and shear are used for cutting through the trunks of other types of trees.